1. Field of the Invention
The present invention is directed to air drag reduction devices for vehicles and, more particularly, to air drag reduction apparatus for tractor-trailers which includes left, right and top panels, and in some cases lower, panels, which panels are mounted by hinges on the generally rectangular rear doors of the tractor-trailer and are swingable into an extended drag-reducing position where they are disposed at an inward angle of approximately five to twenty-five degrees from an essentially parallel alignment with the top, bottom and side walls of the tractor-trailer. The device further includes biasing devices such as springs mounted within or adjacent the hinges and which are operative to bias the panels toward and into their extended drag-reducing position and yet permit the panels to pivot between the extended position and a collapsed position where they lie in adjacent and contacting relationship relative to the rear trailer doors. The arrangement is such that if and when one or more of the panels might come into impacting relationship with an external object, such as a freight dock or another truck body, damage to the panels is significantly reduced as a result of the fact that the panels are collapsibly mounted on the rear doors.
2. The Prior Art Background
Operation of tractor-trailer units involves significant expenditures for maintenance and upkeep, but the single most costly element of operation is almost certainly the fuel costs required to operate the tractor-trailer. One of the operational features which most significantly increases the fuel consumption cost is that the tractor-trailer, as commonly used, has an extremely inefficient aerodynamic shape, since the size and shape of the tractor-trailer is generally dictated by the amount of cargo and size and shape thereof which the tractor-trailer needs to carry. Therefore, a large rectangular box shape is generally used for the trailer unit because such shape is most conducive to loading and unloading and carrying of cargo therein. However, it is also well-known that the rectangular box shape is extremely aerodynamically inefficient, and it is not only the forward flat front of the trailer which presents aerodynamic inefficiencies, but the rear of the trailer likewise is aerodynamically inefficient due to the large amount of turbulence and drag produced by air flowing over the top, bottom and sides of the trailer and onto the squared-off rear end. Particularly due to ever-increasing fuel prices, improvement of the aerodynamics of the tractor-trailer is becoming ever more important, and therefore there is a need to improve the aerodynamic performance of the tractor-trailer unit.
Many different inventions have been proposed in the prior art which attempt to address and solve this problem. For example, Roberge et al., in U.S. Pat. No. 6,485,087, disclose a panel configuration for attachment to the rear of a tractor-trailer which is designed to significantly reduce the turbulence and drag produced by the rear of the unadorned trailer. However, while Roberge et al. do provide one form of solution to the aerodynamic problem, their design raises other problems, namely, what happens when, inevitably, the panels encounter an external object such as a loading dock or another vehicle? As taught in the Roberge et al. patent, specifically in FIG. 9 thereof, a rubber flexible material may be applied to the leading edge of the panel to lessen the damage caused by the impact. Of course, such a rubber flexible edge will be of little use when the panel encounters a loading dock or the like, and it is clear that in such an instance the impact will cause a great deal of damage to the aerodynamic panel.
Many other devices have been proposed in the prior art which also incorporate aerodynamic panels on the rear of the tractor-trailer, but not a single one of these addresses the issue of what might occur when the panel impacts a loading dock or the like, as will inevitably occur when the tractor-trailer is being backed into a loading and unloading location. While some of the devices apparently teach the manual movement of the panels to a storage position prior to opening the rear doors and loading and/or unloading the trailer, this does not fully address the question of what might occur if the driver or loading dock personnel simply forget to move the panels to their storage position. Therefore, there is a significant need for an aerodynamic panel device which will not only function to significantly reduce the cost of operating the tractor-trailer, but which also addresses and solves the question of what might occur when the panels accidentally impact an external object such as a loading dock or the like.
Therefore, an object of the present invention is to provide an improved air drag reduction apparatus for tractor-trailers whereby damage to the aerodynamic panels caused by non-ballistic impact with external objects is significantly reduced and/or eliminated.
Another object of the present invention is to provide an improved air drag reduction apparatus for tractor-trailers which includes left, right and top panels, and for some applications bottom panels, which panels are mounted by hinges directly on the rear doors of the trailer, the panels and which extend rearwardly, when deployed, into an extended drag-reducing position at an inward angle of approximately five to twenty-five degrees relative to the planes defined by the top, bottom and sides of the tractor-trailer.
Another object of the present invention is to provide an improved air drag reduction apparatus for use with tractor-trailers which includes stop devices such as cables or hinge stops which hold the panels in an extended position to generally ensure that the proper angle of orientation is maintained during operation of the tractor-trailer.
Another object of the present invention is to provide such an improved air drag reduction apparatus for use with tractor-trailers that includes biasing devices which are associated with the panels, which are operative to bias the panels outwardly and rearwardly toward and into their extended positions, and which are further operative to permit each of the panels to pivot between the extended position towards and into a collapsed position when and if the panels come into contact with an external object. In accordance with the invention, the panels then are free to return to the extended position substantially immediately when such contact with an external object is discontinued. With such apparatus, damage to the left, right, top and bottom panels caused by impact with the external object may be significantly reduced or eliminated. As explained in further detail herein below, because of the novel arrangement provided by the invention, it is not always necessary to bias the side panels using directly attached biasing devices. Rather, in a preferred embodiment, the cooperative interaction between the panels causes the upwardly biased upper panels to apply an outwardly directed bias to the associated side panels.
Finally, an object of the present invention is to provide an improved air drag reduction apparatus for use with tractor-trailers which is relatively simple and durable in design and construction and is safe, efficient and effective in use.